A Rapidly Growing Cardiac Mass—Malignant or Benign?

Graphical abstract


INTRODUCTION
Primary cardiac tumors occur infrequently, with an incidence of 0.0017% to 0.19% according to an autopsy series performed in nonselected populations. 1,2 Secondary cardiac tumors (usually metastases to the heart) outnumber primary cardiac tumors 20 to 1. Cardiac myxomas, often called the ''great masquerader,'' are the most common among them, with an annual incidence of 0.5 to 1 case per million. 3 Signs and symptoms of myxomas usually depend on their size, mobility, and location. The triad of embolism, intracardiac obstruction, and constitutional symptoms is the classic clinical manifestation of cardiac myxoma. 4 Transthoracic (TTE) and transesophageal (TEE) echocardiography is often the first-line imaging technique for the diagnosis of cardiac masses, with TEE yielding a higher sensitivity of 100% versus 95%. 5 Other modalities such as cardiac computed tomography (CCT) or cardiovascular magnetic resonance (CMR) are used if diagnostic confusion persists after TTE or TEE as they provide superior anatomical delineation of cardiac masses.
Here we describe a rare case of a rapidly growing left atrial (LA) myxoma presenting as heart failure and the role of multimodality cardiac imaging in confirming the diagnosis and planning the preoperative management.

CASE PRESENTATION
A 51-year-old woman presented with progressive shortness of breath and lower extremity edema for 1 week. Physical exam revealed pulmonary congestion, elevated jugular venous pressure, 2+ leg edema, a grade 2/6 diastolic murmur, and an early diastolic ''plop'' at the apex. Transthoracic echocardiography showed a large LA mass with diastolic prolapse into the left ventricle (LV) causing severe mitral stenosis (mean gradient, 25 mm Hg; Figure 1A and B). Left ventricular (LV) ejection fraction was 58%, and pulmonary artery systolic pressure was 62 mm Hg. Transesophageal echocardiography showed a 6.0 Â 5.8 Â 2.9 cm encapsulated mass that occupied almost the entire left atrium (LA; Figure 1C and D, Videos 1 and 2). M-mode and color flow Doppler showed significant LV inflow obstruction ( Figure 1E).
The mass was attached to the atrial septum at the fossa ovalis by a short stalk. Cardiac magnetic resonance imaging showed that the mass was isointense on T1-weighted images with no fat suppression and hyperintense on T2-weighted images and had extensive, heterogenous late gadolinium enhancement (LGE; Figure 1F and G, Videos 3 and 4). A TTE performed 9 months prior showed no mass, indicating a very rapid growth rate of $6 mm/month ( Figure 1H, Videos 5-7). The patient underwent complete surgical excision of the mass, which was soft and gelatinous appearing with scattered hemorrhages. Histopathology showed characteristic lepidic, polygonal cells in a loose, myxoid stroma confirming the diagnosis of myxoma ( Figure 1I and J, Video 8). Thirteen months after surgery, the patient is asymptomatic and doing well.

DISCUSSION
There are very rare case reports of rapidly growing LA myxomas, however, not to this size in this short a span of time or rate of growth VIDEO HIGHLIGHTS Video 1: Two-dimensional TEE, midesophageal zoomed 4chamber view (0 ) with color flow Doppler demonstrates the large LA mass obstructing the mitral valve outflow. Video 2: Two-dimensional TEE, transgastric short-axis (0 ) view at the level of mitral valve demonstrates the large LA mass completely obstructing the mitral valve. Video 3: Cardiovascular magnetic resonance steady-state free precession sagittal short-axis display at the level of the aortic valve demonstrates the large LA mass. Video 4: Cardiovascular magnetic resonance steady-state free precession 3-chamber display demonstrates the LA mass attached to the interatrial septum, passing through and obstructing the mitral valve. Video 5: Two-dimensional TTE apical 3-chamber view with color flow Doppler, obtained 9 months prior to this presentation, demonstrates no evidence of LA mass. Video 6: Two-dimensional TTE apical 4-chamber view with color flow Doppler, obtained 9 months prior to this presentation, demonstrates no evidence of LA mass. Video 7: Two-dimensional TTE parasternal long-axis view with color flow Doppler, obtained 9 months prior to this presentation, demonstrates no evidence of LA mass. Video 8: Intraoperative two-dimensional TEE, midesophageal 3-chamber view (130 ) with color flow Doppler, obtained after LA myxoma excision.
(6 mm/month; the average rate of growth is reported to be 1 mm/ month), and none with this degree of LA encroachment and severe mitral stenosis producing rapid heart failure symptoms. 1 Additionally, the absence of any systemic symptoms such as fever, abnormal inflammatory biomarkers (interleukin-6, C-reactive protein), or embolic phenomena with such a large myxoma was unusual. Even though the very rapid rate of growth suggested a malignant neoplasm, other features argued against malignancy, namely, its location in the LA as a solitary lesion with origin in the fossa ovalis, lack of penetration through tissue planes, absence of invasion of the great vessels, myocardium, and pericardium, and no primary neoplasm elsewhere (e.g., in the lungs, kidney, or breast). 6 Table 1 lists features that can help differentiate between benign and malignant cardiac masses. Our patient had no family history of tumors and had a solitary myxoma with no other features of the Carney complex, lentigines, atrial myxomas, and blue nevi, or nevi, atrial myxoma, myxoid neurofibromas, and ephelides syndromes.
Multimodality cardiac imaging assists in tumor characterization and plan preoperative management. Aside from providing a comprehensive assessment of cardiac function and structure, CMR is uniquely suited to provide noninvasive tissue characterization of masses. Cardiac myxomas frequently have high signal intensity on T2 imaging due to their high water content (myxoid elements) and display heterogenous high signal on LGE sequences. Occasionally, thrombi on the surface of the myxoma can produce a low signal intensity on the exterior of the mass. 7 Parametric mapping can help differentiate between the various components of a mass such as fat, iron, lipid, melanin, blood, fluid, and fibrous tissue. Cardiac computed tomography is the imaging modality of choice for the detection of calcification and can provide complementary information to CMR regarding tissue composition (e.g., cystic elements, fat, hematoma or fresh thrombus, abscess, etc.) and aid in preoperative planning, but it exposes the patient to radiation. 8 Positron emission tomography (PET) can detect tumors (which are usually hypermetabolic), inflammation, and infection, and thus it can be useful to detect infections on implanted devices, endocarditis, or inflammatory conditions (sarcoidosis, vasculitis). Despite advances in various cardiac imaging modalities, echocardiography remains the first line in the evaluation of cardiac masses. Echocardiography has the advantage of having excellent temporal resolution (10 ms compared to 25 ms for CMR and 75-125 ms for CCT)  and is preferred for small, mobile structures (such as vegetations or papillary fibroelastomas), which may be missed by CMR or CCT. Additional advantages are that it is portable and widely available. Left-sided cardiac myxomas are managed with surgical excision, with an operative mortality of under 0.5% and a risk of recurrence of 2% to 5%.

CONCLUSION
One should not judge a cardiac mass solely based on its growth rate but apply a comprehensive approach incorporating all the clinical and imaging information available. This increases the predictive accuracy for noninvasive characterization of cardiac masses. Nonetheless, histology remains the gold standard.

CONSENT STATEMENT
Complete written informed consent was obtained from the patient (or appropriate parent, guardian, or power of attorney) for the publication of this study and accompanying images.